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TPS65135: The output negative (VO(NEG)) with load output current is too small and the device does not work

Lumina Gui
Genius 3780 points
Part Number: TPS65135
Other Parts Discussed in Thread: TPS65132

I used the TPS65135RTE for my power circuit design. The nominal output positive (Vo(ops)) and output negative (VO(NEG)) with load current can reach 80mA according to the data sheet, but I only used about 30mA for the actual work of my display screen, but TPS65135 output with the load of the display screen doesn't work normally.

I used the multimeter series circuit to test and found that the output negative(Vo(NEG)) load capacity was only about 22mA. So there was the problem of screen jitter.

I have attached my design circuit to the attachment, and want to know the reasons for this problem.

  • 0
    TI__Mastermind 18550 points

    Hello,

    I reviewed your schematics and the only adjustment I would recommend is to to use a 2.2uH inductor. Higher inductor value can impact output current capability and transient response so please use a 2.2uH inductor as recommended in the typical application schematics in the datasheet.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Genius 3780 points

    Hi Liaqat,

    I tried replacing the L2 inductor with 2.2uH, but the problem still exists.  I also tried to remove R174 and R177, and it doesn't work yet.

    Can I use TPS65132B0 to replace TPS65135 for the my power circuit design?

    Thanks,

    Best Regards

  • 0 in reply to Lumina Gui
    TI__Mastermind 18550 points

    Hi Lumina,

    Your design looks correct schematically so I am not sure why you are not getting more than 30mA.

    If you draw more than 30mA, does the output voltage start to drop? or what happens?

    If there is no load (i.e. you disconnect the display) do you get correct voltage at AVDD_LCD and AVEE_LCD nodes?

    If you do get correct voltage when there is no load, can you please connect load after the device has powered up and has correct voltage at the output. I would like to understand why you can not get the proper load current.

    To answer your other question, yes you can use a device from TPS65132 family but the device I would recommend for your application need is TPS656132B5.

    Kind Regards,

    Liaqat